The present invention relates to an impactor-type separator for separating particulate material from fluid.
Impactor separators for separating particulate material from fluid are known in the art. Generally, such separators provide for causing gas containing particulate material to be fed from a conduit and to impinge upon an impaction plate. A portion of the particulate material adheres to the plate and the gas continues along its flow path for further treatment.
One known prior art device is described in U.S. Pat. No. 4,006,938 which relates to distributing fibrous material into a silo while separating the material from the air flow used as the carrier medium. In this patent, an air-fibrous material is fed from a conduit and is caused to impinge upon the surface of a flat rotating disc. Such disc comprises a perforated portion. In operation, a suction conduit draws the air of the air-fibrous material through the disc perforations. The combined action of the material impacting upon the disc surface and the centrifugal force generated by a high rotational speed of the disc, allows that fibrous material gathered upon the portion of the disc which is not perforated to fall from the disc and be collected as desired in a silo. The efficiency of devices of this type is dependent in part upon providing an adequate seal between the feeding conduit and the suction conduit so that the suction force draws the air through the disc perforations rather than draw some of the air-fibrous material around the edge of the disc. In addition, in view of the existence of perforations, the collecting or impacting surface is not continuous but rather is interrupted by such perforations. In such structure the size of the perforations must be such as to allow the air to pass through without also allowing the fibrous material to pass through. Accordingly, such devices are not particularly useful when the particles are micron-size since such small particles will pass through the perforations along with the air carrier.
The use of an impact rotary disc-like separator has also been used in filtering dust from air and in similar applications. In many applications very large quantities of gas must be cleaned. Prior to the use of rotary separators in such applications, use was made of conventional fiber mat filters. However, the impact efficiencies of the individual fibers are low at relatively low gas velocities. In use, acceptably high values are obtained by allowing the gas to pass over a large number of fibers such as are provided in the fiber mat filters. However, the use of a large number of fibers increases the resistance of the filter and decreases the gas flow velocity.
Improvements upon the fiber mat filters have been directed to increasing gas velocity to increase impaction efficiency so that few fibers are required thereby decreasing the resistance of the filter. To this end, known prior art includes fibers or filaments mounted radially like spokes from a hub of a disc. Rotation of the disc in a plane perpendicular to the gas flow allows the gasborne particles to impact upon the filaments and allows centrifugal force to remove such impacted particles in contact with the filaments so that such particles may be collected as desired. Varying applications may use such impact filters. However, in certain applications it may be necessary to increase the number and diameter of the radially oriented filaments to such an extent as to undesirably increase the resistance of the filter and decrease the gas flow velocity. In addition, when solid particles are to be removed, it is necessary to moisten the filament. Separators of the foregoing type are described in British Pat. No. 1,144,872.
In one known prior art device particle laden air is drawn into such device and is accelerated through a converging nozzle of a first impactor stage. Particles leaving the nozzle separate into two portions. A first portion has sufficient inertia to impact upon the surface of a first drum. A second portion having less inertia flows with the air streamline to a second converging nozzle and the process is repeated. A plurality of converging nozzles each having a successively smaller slit width is provided in association with a plurality of successive drums. By successively decreasing nozzle slit width the air passing through the nozzles is accelerated to progressively higher velocities to remove smaller particles. However, as the air continues through the device there is a tendency for particulate material previously collected upon the drums to be dislodged by such air since the drum surface continues to lie in the direct path of the gas stream even after moving from a position adjacent to a converging nozzle.
In the apparatus described in U.S. Pat. No. 4,118,207, particulate laden gas, such as lint laden air in a clothes dryer, flows from an inlet conduit and engages the surface of a plurality of spaced discs having hollow portions adjacent the centers thereof. The gas passes through the spaces between the discs and through the hollow portions for discharge as desired. The lint moves adjacent the peripheries of the discs to be discharged through a discharge conduit. In such devices, the existence of the spaces between the discs provides a structure in which the collecting or impacting surface is interrupted by such spaces. Accordingly, such devices are not particularly useful when the particles are micron-size since such particles will pass from the inlet conduit directly to the spaces between the discs, and then to the hollow portions, along with the air carrier.
Other known devices are for use in various applications to collect particles from a gas stream so that the particles can be measured for size. An example of such use occurs in air pollution studies. For example, U.S. Pat. No. 3,983,743 describes impactors having a radial slot design. Such impactors are stacked to form a multistage cascade of impactors. In such a device, particulate laden gas flows through radial slots in a first impactor stage and larger particles impact on the first collection substrate. Then, the air-stream flows through the narrower slots in the second impactor stage, and smaller particles impact on the second collection substrate. The air flow continues and the radial slots in succeeding impactors are smaller at each succeeding stage. By providing radial slots, a circumferential flow pattern is created between impactor stages. As the air flow progresses through the device the resistance to such flow increases.
Accordingly, it is an object of this invention to provide a separator requiring no sealing mechanism between the inlet through which the particle laden gas flows and the outlet through which the cleaned gas flows.
Yet another object of this invention is to provide a separator in which the particle laden gas continuously impacts upon a collecting surface during operation of the apparatus.
Still another object of this invention is to provide a separator useful in separating micron-size particles from a gas.
A further object of this invention is to provide a separator which includes a particle collector which does not increase the resistance to gas flow causing a decrease in gas flow velocity to the extent of many prior art devices and yet which may be used in separating micron-size particles from a gas.
Still another object of this invention is to provide a separator which does not require the use of a moistener when solid particles are removed from a gas.
Another object of this invention is to provide a separator in which collected particulate material is not removed from the collector, and deposited back into the gas stream, by the flow of the gas through the apparatus after the collector moves from a position adjacent the inlet for the particle laden gas.
Another object of this invention is to provide a separator having an inlet for particle laden gas which is continuously adjacent to and substantially encompassed by a closed area of a collector.